(1) Field of the Invention
The present invention relates to a process for preparing a modified molding material by blending a methacrylic polymer composition with a modifying polymer in an extruder.
(2) Description of the Related Art
A process comprising blending a methacrylic polymer composition with a modifying polymer by a Henschel mixer, a tumbling mixer or the like and extruding the blend is generally known. This process however, has a problem in that, when a modifying polymer is blended into a methacrylic polymer composition containing a large quantity of a volatile component and the blend is extruded, the modifying polymer is deposited on the wall surface of an apparatus or bridging of polymer particles occurs in a hopper, and therefore, it is difficult to stably supply polymers at a constant rate.
Japanese Unexamined Patent Publication No. 50-43166 proposes a vented extruder suitable for incorporating an additive such as an antioxidant or an ultraviolet absorber into a methacrylic resin flowing through the vented extruder. In this extruder, an additive-inlet is provided in a barrel between a final vent hole and an extrusion die.